[leetCode/JS] 13. Roman to Integer

문제 설명

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

For example, 2 is written as II in Roman numeral, just two ones added together. 12 is written as XII, which is simply X + II. The number 27 is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

• I can be placed before V (5) and X (10) to make 4 and 9.
• X can be placed before L (50) and C (100) to make 40 and 90.
• C can be placed before D (500) and M (1000) to make 400 and 900.

Given a roman numeral, convert it to an integer.

 

 

입출력 예

Example 1:

Input: s = "III"
Output: 3
Explanation: III = 3.

 

Example 2:

Input: s = "LVIII"
Output: 58
Explanation: L = 50, V= 5, III = 3.

 

Example 3:

Input: s = "MCMXCIV"
Output: 1994
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

 

Constraints

• 1 <= s.length <= 15
• scontains only the characters ('I', 'V', 'X', 'L', 'C', 'D', 'M').
• It is guaranteed that s is a valid roman numeral in the range [1, 3999].

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내 솔루션

• 로마자를 받아서 switch case로 하다가 아 바본가! 하면서 object로 map을 만들어서 했다.
• 현재 나보다 큰 숫자가 나오면 뺀다 라는 것을 알아내면 나머진 일사천리!

var romanToInt = function(s) {
  const romans = {
    'I': 1,
    'V': 5,
    'X': 10,
    'L': 50,
    'C': 100,
    'D': 500,
    'M': 1000,
  }
  let sum = 0;
  for(let i = 0; i < s.length; i++) {
    if(romans[s[i]] < romans[s[i+1]]) sum -= romans[s[i]];
    else sum += romans[s[i]];
  }
  return sum;
};

감상평

• 실제로 실용적인 문제를 푼거 같아서 매우 맘에든다.
• 나중에 다른 솔루션들을 봤는데 나랑 똑같이 푼사람들이 좀 있는 것 같다. 신기해